Defense Secretary Ashton B. Carter said Thursday that he is opening all jobs in combat units to women, a landmark decision that would for the first time allow female service members to join the country’s most elite military forces.

Women will now be eligible to join the Navy SEALs, Army Special Forces and other Special Operations Units. It also opens the Marine Corps infantry, a battle-hardened force that many service officials had openly advocated keeping closed to female service members.

“There will be no exceptions,” Carter said. “This means that, as long as they qualify and meet the standards, women will now be able to contribute to our mission in ways they could not before.”